Planting date, water availability and plant density effects on dry bean production (Phaseolus, vulgaris L.) NOKUTHULA CHERRY HLANGA Submitted in fulfilment of the academic requirements of Master of Science in Agriculture Crop Science School of Agricultural, Earth & Environmental Sciences College of Agriculture, Engineering and Science University of KwaZulu-Natal Pietermaritzburg South Africa March 2017
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Planting date, water availability and plant density effects on dry
bean production (Phaseolus, vulgaris L.)
NOKUTHULA CHERRY HLANGA
Submitted in fulfilment of the academic requirements of
Master of Science in Agriculture
Crop Science
School of Agricultural, Earth & Environmental Sciences
College of Agriculture, Engineering and Science
University of KwaZulu-Natal
Pietermaritzburg
South Africa
March 2017
i
PREFACE
The research contained in this thesis was completed by the candidate while based in the Discipline
of Crop Science, School of Agricultural, Earth and Environmental Sciences, in the College of
Agriculture, Engineering and Science, University of KwaZulu-Natal, Pietermaritzburg Campus,
South Africa. The research was financially supported by the Water Research Commission (WRC)
of South Africa through WRC Project No. K5/2272//4 ‘Determining water use of indigenous grain
and legume food crops’.
The contents of this work have not been submitted in any form to another university and, except
where the work of others is acknowledged in the text, the results reported are due to investigations
by the candidate.
_________________________
Signed: Professor Albert T. Modi
Date: 13 March 2017
ii
DECLARATION
I, Nokuthula Cherry Hlanga, declare that:
(i) the research reported in this dissertation, except where otherwise indicated or acknowledged, is my original work;
(ii) this dissertation has not been submitted in full or in part for any degree or examination to any other university;
(iii) this dissertation does not contain other persons’ data, pictures, graphs or other information, unless specifically acknowledged as being sourced from other persons;
(iv) this dissertation does not contain other persons’ writing, unless specifically acknowledged as being sourced from other researchers. Where other written sources have been quoted, then:
a) their words have been re-written but the general information attributed to them has been referenced;
b) where their exact words have been used, their writing has been placed inside quotation marks, and referenced;
(v) where I have used material for which publications followed, I have indicated in detail my role in the work;
(vi) this dissertation is primarily a collection of material, prepared by myself, published as journal articles or presented as a poster and oral presentations at conferences. In some cases, additional material has been included;
(vii) this dissertation does not contain text, graphics or tables copied and pasted from the Internet, unless specifically acknowledged, and the source being detailed in the dissertation and in the References sections.
______________________
Signed: Nokuthula Hlanga
Date: 13 March 2017
iii
ABSTRACT
Dry beans (Phaseolus vulgaris L.) form an important part of the agricultural system in southern
Africa. Small scale farmers use the crop in crop rotation or intercropping with another staple crop,
maize. Although commercial seeds are not retained for use from one season to another, small-scale
farmers do keep grain seed for reasons of germplasm preservation and economic reasons. It is
important to understand the effect of some of the major agronomic factors on seed quality and crop
performance in a situation where farmers retain seed from one season to another without using
special seed storage methods. The objective of this study was to determine the effect of planting
date, water availability and plant density on dry bean growth and yield using seed lots from
subsequent generations of three dry bean varieties (Mtata, Malelane and Gadra). Dry beans
subsequent seed quality varied significantly (P<0.05) among varieties, with Mtata, Malelane and
Gadra having varied responses when subjected to varied agronomic conditions. All of the seed
quality test indices varied significantly (P<0.05) among seed varieties, plant density, and water
availability. Seed germination, germination velocity index (GVI), and mean germination time
(MGT) were higher under rain-fed relative to irrigated conditions. This showed that dry bean
varieties could be produced under water-limited conditions and produce relatively good seed
quality. Field growth parameters were highly influenced and varied among agronomic management
practices (dry bean varieties, plant density, season, and water availability). The three dry bean
varieties Mtata, Malelane and Gadra had varied responses when subjected to varied agronomic
conditions. Growth and yield parameters differed significantly (P<0.05) with planting date and
water availability. Planting date (season), and water regime had considerable impact on growth and
yield parameters. The highlight of the study was that the agronomic management practices have an
important influence on crop growth and yield of dry bean crop. Although seed quality was
statistically similar for the initial and post-harvest seed lots. Crop performance was better in the
summer early season (January to April) when compared with the late season (May to August).
Therefore, this study recommends that seed can be retained from previous harvest without
significant loss of quality; however, careful selection of planting date is necessary to get optimum
crop performance.
iv
ACKNOWLEDGMENTS
A number of special acknowledgements deserve specific attention:
• The Water Research Commission of South Africa is acknowledged for funding through
WRC Project No. K5/2272//4 ‘Determining water use of indigenous grain and legume food
crops’,
• Prof Albert Thembinkosi Modi, my supervisor, for providing me with this opportunity to
further my studies and for his continuous guidance throughout my studies,
• Dr. Tafadzwa Mabhaudhi, for the support and guidance during the course of the study
• My mentor, Vimbayi Chimonyo, for always being there to assist me
• The ‘Green Team’ (Sandile, Delight, Tendai, Silindile, Nomthandazo, Ntokozo and Pretty)
for their assistance during the course of my studies,
• The Ukulinga staff for their assistance during my field trials, (Ma’ Florence, Nosipho,
Nokulunga, Baba Zuma, and Sis Thembi)
• My family and friends for their amazing support throughout my studies, especially my
parents for their patience and courage.
v
CONTENTS
PREFACE ......................................................................................................................................... i
DECLARATION ............................................................................................................................. ii
ABSTRACT ................................................................................................................................... iii
ACKNOWLEDGMENTS .............................................................................................................. iv
LIST OF TABLES ......................................................................................................................... ix
LIST OF FIGURES ......................................................................................................................... x
Figure 4. 1: A comparison of final germination percentage for three dry bean varieties (Mtata, Gadra and Malelane). Standard error bar represent standard deviation (±4.32).
4.2.2 Pre-planting germination velocity index (GVI)
There were significant differences (P=0.027) observed for germination velocity index (GVI) for
three dry bean varieties. The trend for germination velocity index was Mtata (24) > Gadra (23.1) >
Malelane (21.9) (Figure 4.2) (Appendix 2).
10
20
30
40
50
60
70
80
90
100
Gadra Malelani Mtata
Ger
min
atio
n (%
)
Cultivar
P= 0.027; LSD (P>0.05) = 8.64; CV%= 6.6
29
Figure 4.2: A comparison of germination velocity index (GVI) for the three dry bean varieties (Mtata, Gadra and Malelane). Standard error bar represent standard deviation (±1.10).
4.2.3 Post planting germination percentage
There was a significant difference (P<0.05) for germination percentage with regards to the
interactions of water regime x plant density x variety x time interaction. Overall, across the water
regimes and plant densities (Figure 4.3, A, B, C, D, E, and F), Gadra had the lowest germination
(28.30%) and Malelane the highest germination (98.80%). Similarly, under the two water regimes
irrigated (Figure 4.3, A, B and C) and rain-fed (Figure 4.3, D, E and F), Malelane had the highest
germination (98.80%) and Gadra the lowest germination percentage (31.70%). Medium density
(Figure 4.3, B and E) had the highest germination % (93.20%) while high density (Figure 4.3, C
and F) had the lowest germination percentage (74.30%). With respect to variety Mtata and
Malelane showed the highest seed germination (88.50%) while Gadra showed the lowest
germination (78.70%) (Appendix 3).
0
5
10
15
20
25
30
Gadra Malelani Mtata
Ger
mia
ntio
n V
eloc
ity In
dex
(GV
I)
Cultivar
P= 0.027; LSD(p>0.05)=2.2; CV=6.6%
30
Figure 4.3: A comparison of final germination percentage for three dry bean varieties (Mtata, Gadra and Malelane) under different water regimes (rain-fed and irrigated), and plant densities (high, medium and low). A = irrigated low density, B = irrigated medium density, C = irrigated high density, D = rain-fed low density, E = rain-fed medium density, F = rain-fed high density.
31
4.2.4 Post planting Germination Velocity Index (GVI)
Germination Velocity Index (GVI) showed that there was a significant difference (P<0.05) for the
interaction of water regime x plant density x variety (Appendix 4). Overall, the mean GVI for the
dry bean varieties were 2.57, 2.47 and 2.57 for Malelane, Mtata and Gadra respectively (Figure
4.4). Germination Velocity Index showed that seeds harvested from maternal plants grown under
irrigated conditions had higher GVI compared to under rain-fed conditions. Medium planting
density had the highest GVI (3.56) relative to low planting density (2.51) and high planting density
(2.19).
Figure 4. 4: A comparison of Germination Velocity Index (GVI) for three dry bean varieties (Mtata, Gadra and Malelane), under different water regimes (rain-fed and irrigated), and plant densities (high, medium and low). Standard error bar represent standard deviation (±0.71).
4.2.5 Post planting mean germination time (MGT)
There were significant differences (P=0.01) observed for the mean germination time (MGT) for
the interaction of water regime x plant density x variety (Appendix 5). Gadra had the lowest MGT
respectively to Mtata and Malelane, Malelane (0.44 days) > Mtata (0.42 days) > Gadra (0.36 days).
Under irrigation, MGT was lower (0.35 days) relative to when dry beans were grown under rain-
0
1
2
3
4
Gadra Malelani Mtata Gadra Malelani Mtata
Rain-fed Irrigated
Gem
inat
ion
velo
city
inde
x (G
VI)
Water regime
P= 0.01; LSD(P>0.05) = 1.43; CV=15.4
Low Medium High
32
fed conditions (0.39 days). For three plant densities MGT was observed to be higher under high
density (high density (0.42 days) >, medium density (0.4 days) >, and low density (0.38 days).
Across all treatment combinations, Malelane under irrigation, and medium density had the highest
MGT, and the lowest MGT was seen for Malelane under low density under irrigated conditions
(Figure 4.5).
Figure 4.5: A comparison of Mean Germination Time (MGT) for three dry bean varieties (Mtata, Gadra and Malelane) under different water regimes (rain-fed and irrigated), and plant densities (high, medium and low). Standard error bar represent standard deviation (± 0.025).
4.2.6 Post planting seed moisture content (%)
An interaction of plant density and cultivar had significant effect (P=0.041) on dry bean seed
moisture content. Planted under the low density treatment had the lowest seed moisture content
(9.90%) relative to high (10.10%) and medium (10.20%) (Appendix 6). There was no significant
difference (P > 0.05) between the three dry bean varieties Gadra (10.00%), Malelane (10.10%),
and Mtata (10.00%). The treatment combination of variety (Malelane) and medium plant density
0
0.1
0.2
0.3
0.4
0.5
0.6
High Low Medium High Low Medium
Dryland Irrigated
Mea
n G
erm
inat
ion
Tim
e (M
GT
) (D
ays)
Cultivar
P = 0.01; LSD (P>0.05) = 0.05; CV%= 4.80
Gadra Malelani Mtata
33
had the highest seed moisture content compared to the low and high plant densities. Overall Mtata
variety under high plant density showed highest grain moisture (Figure 4.6).
Figure 4. 6: A comparison of seed moisture content (%) for three dry bean varieties (Mtata, Gadra and Malelane) under different three plant densities (low, medium and high density). Standard error bar represent standard deviation (±0.16).
9
9.2
9.4
9.6
9.8
10
10.2
10.4
10.6
Gadra Malelani Mtata
Moi
stur
e co
nten
t (%
)
Cultivar
P = 0,041; LSD(P<0,05) = 0,32; CV% = 2,1
High Low Medium
34
4.2.7 Post planting water activity
There were highly significant differences (P=0.001) observed for the seed water activity for the
interaction of water regime x variety (Appendix 7). Seeds harvested from maternal plants grown
under irrigated conditions had the lowest water activity (0.52) when compared with rain fed field
(0.54) (Figure 4.7). The treatment combination of variety x water regime, seeds of Mtata harvested
under rain-fed conditions had the highest water activity relative to irrigated field. While Gadra
under irrigated conditions had the lowest water activity (Figure 4.7).
Figure 4. 7: A comparison of water activity for three dry bean varieties (Mtata, Gadra and Malelane) under different two water regimes (rain-fed and irrigated). Standard error bar represent standard deviation (±0.0045).
0.48
0.49
0.5
0.51
0.52
0.53
0.54
0.55
0.56
Gadra Malelani Mtata
Wat
er a
ctiv
ity
Cultivar
P = 0,001; LSD(P<0,05) = 0,009; CV% = 2,1
Rain-fed Irrigated
35
4.3 Discussion
Significant differences (P<0.05) were observed under pre-planting and post planting germination
results among the dry bean seeds varieties. This confirms that studied dry bean seed varieties had
an influence on the subsequent seed quality. This could because of the genetic differences amongst
the dry bean seed varieties (Elballa et al., 2015). Initially, Mtata variety had the highest percentage
seed germination but Malelane had the highest percentage germination post-planting. This shows
that subsequent dry bean seed quality was affected environmental factors due to maternal plant
(Akibode and Maredia, 2012).
Seeds produced under rain-fed conditions had high germination percentage over a short period.
Germination velocity index was higher under rain-fed conditions when compared with under
irrigated conditions. Mean germination time was lower under rain-fed conditions meaning that the
subsequent seeds were able to germinate faster than those from the irrigated trial. This could
suggest that limited water availability subsequent seed quality could actually be enhanced (Ahmad
et al., 2009). Under water limited conditions, adaptable seed will aim to germinate and establish
quickly to take advantage of available water (Ghassemi-Golezani and Mazloomi-Oskooyi, 2012).
It could be that the reduction in pod number and average seed number per pod under water stress
conditions helps maintain seed integrity with regards to seed quality (Odindo, 2010). It was
observed also that under the lower plant densities the seed quality indices were low. This implies
that planting dry bean under low plant density has no favourable gain on seed quality but only on
grain yield.
4.4 Conclusion
In the present study, subsequent dry bean seed quality varied among different management
practices. Mtata, Malelane and Gadra dry bean varieties varied in their responses to the varied
agronomic conditions. Seed germination, GVI, and MGT were favourable under rain-fed
conditions. This implies that dry bean seed can be grown under rainfed conditions for the purposes
of seed without adverse effects on the quality (germination and vigour) of the seed. The study also
highlights the importance of the correct combination of management practices in which the
maternal plants are exposed for good quality seeds.
36
References
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annuus L.) response to drought stress at germination and seedling growth stages. Pakistan Journal
of Botany, 41, 647-654.
Ahmadi, M. and Bahrani, M. 2009. Yield and yield components of rapeseed as influenced by water
stress at different growth stages and nitrogen levels. American-Eurasian Journal of Agricultural
and Environmental Sciences, 5, 755-761.
Akibode, S. and Maredia, M. K. 2012. Global and regional trends in production, trade and
consumption of food legume crops, Department of Agricultural, Food, and Resource Economics,
Michigan State University.
Azadi, H., Samiee, A., Mahmoudi, H., Jouzi, Z., Rafiaani Khachak, P., De Maeyer, P. and Witlox,
F. 2016. Genetically modified crops and small-scale farmers: main opportunities and challenges.
Critical Reviews in Biotechnology, 36, 434-446.
Elballa, M., El-Amin, A., Elamin, E. and Elsheikh, E. A. 2015. Interactive effects of varieties,
foliar application of micronutrients and rhizobium inoculation on snap bean (Phaseolus vulgaris
L.) performance. Journal of Agricultural and Environmental Sciences, 50, 555-612.
Ghassemi-Golezani, K. and Hosseinzadeh-Mahootchy, A. 2009. Changes in seed vigour of faba
bean (Vicia faba L.) varieties during development and maturity. Seed Science and Technology, 37,
713-720.
Ghassemi-Golezani, K. and Mazloomi-Oskooyi, R. 2012. Effect of water supply on seed quality
development in common bean (Phaseolus vulgaris var.). International Journal of Plant
Production, 2, 117-124.
Joshi, S. and Rahevar, H. 2014. Effect of dates of sowing, row spacings and varieties on growth
attributing characters of rabi Indian bean (Dolichos lablab L.). Trends in Biosciences, 7, 3717-
3721.
Kheira, A. A. A. and Atta, N. M. 2009. Response of Jatropha curcas L. to water deficits: Yield,
water use efficiency and oilseed characteristics. Biomass and Bioenergy, 33, 1343-1350.
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Kruger, H. S., Steyn, N. P., Swart, E. C., Maunder, E. M., Nel, J. H., Moeng, L. and Labadarios,
D. 2012. Overweight among children decreased, but obesity prevalence remained high among
women in South Africa, 1999–2005. Public health nutrition, 15, 594-599.
Lee, J., Gereffi, G. and Beauvais, J. 2012. Global value chains and agrifood standards: challenges
and possibilities for smallholders in developing countries. Proceedings of the National Academy
of Sciences, 109, 12326-12331.
Mirzaienasab, M. and Mojaddam, M. 2014. The effect of planting date on yield and yield
components of two red bean cultivars in Azna weather conditions. Indian Journal of Fundamental
and Applied Life Sciences, 4 (3), 417-422.
Müller, M., Siles, L., Cela, J. and Munné-Bosch, S. 2014. Perennially young: seed production and
quality in controlled and natural populations of Cistus albidus reveal compensatory mechanisms
that prevent senescence in terms of seed yield and viability. Journal of Experimental Botany, 65,
287-297.
Munro, H. N. 2012. Mammalian protein metabolism. Academic press publishers, New York and
London, Volume IV page 23-30.
Odindo, A. O. 2010. Cowpea seed quality in response to production site and water stress. Doctoral
dissertation, University of KwaZulu-Natal, page 45-56.
Trivedi, M. 2013. Biofield and fungicide seed treatment influences on soybean productivity, seed
quality and weed community. Agricultural Journal, 138-143.
Wani, I. A., Sogi, D. S., Shivhare, U. S. and Gill, B. S. 2015. Physico-chemical and functional
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Research International, 76, 11-18.
38
CHAPTER 5
EFFECTS OF WATER STRESS COMBINED WITH DIFFERENT
AGRONOMIC MANAGEMENT PRACTICES ON DRY BEAN GROWTH
PARAMETERS
5.1 Introduction
Proteins play a vital role in human nutrition (Khan et al., 2014). Protein aid in muscle recovery,
reduces muscle loss, builds lean muscle, building block for bones, and cartilage (Wildman et al.,
2016). South Africans residing in rural communities are said to be protein deficient due to low
intake of complete proteins high in amino acids in their diets (Khan et al., 2014). Dry beans
(Phaseolus vulgaris) are a protein power house and considered as an important and affordable grain
legume (Wheeler and Von Braun, 2013).
A large proportion of government investments have focused on promoting cereal production within
smallholder farming (Department of Agriculture, 2016). In 2015/16 season, more than 1.95 million
land hectares were dedicated to maize production and this yield 3.8 million t/ha while only 35 000
ha was under dry bean production yielding 1.03 million t/ha (DAFF, 2016) . This trend also reflects
current production systems within smallholder farming systems which are currently dominated by
cereal based cropping systems therefore, low dry bean productivity.
The observed low yields could be due to the limited knowledge regarding its production in terms
of best agronomic management practices and water stress (Kadyampakeni et al., 2013). Under
optimum agronomic conditions the plants are able to resource the water distribution uniformly for
optimal growth (Joshi and Rahevar, 2014). Water stress has been observed to cause high yield
losses in agricultural systems for small holder farmers (Brevedan et al., 2012). In crop production
water scarcity is a limiting factor for many small scale farming systems in South Africa, and the
world over (Emam et al., 2010). In South Africa, smallholder farmers highly relay on summer
rainfall for dry bean production (Kadyampakeni et al., 2013).
Due to the impacts of climate change and variability, the onset, duration and rainfall intensity,
coupled with the duration and intensity of drought episodes will further increase water stress for
39
dry bean production (Emam et al., 2010). In dry bean stress, has been observed to reduce leaf area,
chlorophyll content, stomatal closure, and accelerated maturity (Emam et al., 2010). It has also
been observed to change protein seed content, seed antioxidant accumulation, plant osmotic
adjustment, hormone composition, cuticle leaf thickness, and leaf inhibition of photosynthesis
(Fenta et al., 2012).
However, dry beans have adaptive mechanisms to adapt under water stress, which include drought
escape, avoidance, and dehydration tolerance (Kadyampakeni et al., 2013). Water-stressed dry
bean have reduced morphological size, leaf area, and leaf area index (LAI) as well as abnormal
opening and closing of stomata (Fenta et al., 2012). Reduction of leaf number and plant height is
considered a phenotypic mechanism for controlling water use efficiency and reducing oxidative
injury under drought stress conditions (Fenta et al., 2012). During water stress osmotic adjustment
is increased to avoid dehydration and hence, improves yield under water stress (Fenta et al., 2012).
However, there are dry bean varieties that are adaptable to high water stress levels (Mirzaienasab
and Mojaddam, 2014). These varieties are able to grow and survive under limited water conditions
and be able to produce yield (Mirzaienasab and Mojaddam, 2014). These varieties have many traits
that are beneficial for survival under drought stress, thereafter, considered advantageous for dry
bean production under drought (Mirzaienasab and Mojaddam, 2014). However, some of the
varieties are still prone to be affected by severe water stress conditions.
Agronomic management practices include the use of adaptable varieties, appropriate planting dates
and plant densities. The use of early maturing and adaptable varieties as a method for drought
escape is practiced. Planting at the optimum planting date aids the plant to take full advantage of
environment, with optimum rains and temperatures for growth (Emam et al., 2010). A study done
by Fenta et al. (2012) showed that the use of adaptable varieties under rain-fed conditions increases
the crops adaptability towards stress, resource partitioning and dry matter production (Sani et al.,
2014). Planting at an appropriate planting date resulted in increased crop growth period, increased
yield and yield components ( pod number and number of grains per pod, 100-grain weight),
(Mirzaienasab and Mojaddam, 2014) for dry bean crop. A study done by Gómez-Plaza et al, (2001)
showed that optimum plant spacing improves water use efficiency, and consequently an increased
quality seed production. However a study done by Ren et al. (2016) showed that under extreme
water stress, crop biomass, grain yield and water use efficiency were significantly low under high
planting density for maize crop.
40
Dry beans are important crop but there is insufficient information and skill as guidelines to aid
increasing dry bean production. Thus, there is need to invest and investigate more on optimum
agronomic management practices that will aid on improving dry bean production. Therefore, the
aim of this study was to determine effect of plant spacing and irrigation regimes on physiological
parameters of three dry bean varieties. With the objectives to evaluate growth and yield parameters
for three bean varieties grown under varying agronomic practices.
Materials and methods are explained in Chapter 3, section 3.3, 3.4.
5.2 Results
5.2.1 Weather and soil water content
5.2.1.1 Weather
During the growing period, average maximum and minimum temperature were 28.95 and 17.16
°C, respectively. The temperature range was 37.48 to 10.3°C. During the growing season, total
rainfall was 341.63 mm while evapotranspiration was 379.26 mm. The rainfall was observed to
have an uneven pattern throughout the growing season. Rainfall received during emergence and
early vegetative stage [35 days after planting (DAP)] was 148.59 mm. During mid- to late
vegetative phase (35 – 49 DAP), 66.55 mm of rainfall was received. During reproductive (49 - 58
DAP) rain was received of 104.90 mm, while, 21.59 mm was received during the maturity periods
(58 – 65 DAP) to harvest periods with 21.59 mm. This rainfall distribution would suggest water
stress during pod maturation.
5.2.1.2 Soil water content
Soil water content for the varieties was 24.47, 24.11, and 23.43% for Gadra, Mtata and Malelane
respectively. Season two showed that soil water content was Mtata (23.12%) > Malelane (22.78%)
> Gadra (21.36%). Season one showed higher soil water content (24.47%) when compared with
season two soil water content (22.33%). Season one soil water content for low plant density was
high (26.00%) compared to medium density (23.16%) and high density (22.52%). Season two soil
water content medium density (23.46%) was high when compared to high density (22.05%) and
low density (21.06%). Season one soil water content under irrigated (24.70%) was relatively high
41
but, rain fed (24.07%), whereas season two showed irrigated was higher (24.96%), than rain-fed
(19.96%).
Table 5. 1: Average volumetric soil water content (% volume) for the two seasons.
Variety Plant density Water regime
*Soil water content (%) season one
*Soil water content (%) season two
Gadra
Low Rain-fed
25.54 21.72 Medium 25.82 18.50 High 22.54 18.28 Low
Irrigated 24.47 22.00
Medium 25.17 24.15 High 23.32 23.62
Malelane
Low Rain-fed
24.97 18.26 Medium 22.04 21.66 High 18.95 19.89 Low
Irrigated 27.62 24.01
Medium 24.70 26.13 High 22.35 26.86
Mtata
Low Rain-fed
26.53 18.00 Medium 21.44 20.41 High 22.35 23.06 Low
Irrigated 27.37 23.40
Medium 24.96 30.00 High 22.45 24.66
Seasonal mean 24.03 22.48 *Values of soil water content were not replicated. Therefore, values presented in the table are means of treatment combinations.
5.2.2 Crop physiology
5.2.2.1 Chlorophyll content
An interaction of variety x water regime had a significant affect (P=0.013) dry bean chlorophyll
content (CCI). Across the planting seasons, the highest chlorophyll content index of 18.9 was
observed for season one relative to season two 8.7. This was due to optimum environmental
conditions of season one relative to season two. Marginal differences for chlorophyll content index
were observed across the planting densities [high (37.32) > medium (35.68) > low (35.35)] and
variety Gadra [(36.99) > Malelane (36.06), Mtata (35.32)] treatments. Gadra had a high CCI
42
(44.20) under high planting density and rain-fed water regime. The lowest CCI (29.11) was
observed under the treatment combination of Mtata x season two x irrigated (Figure 5.1) (Appendix
8).
Figure 5.1: A comparison of chlorophyll content index for three dry bean varieties (Mtata, Gadra and Malelane), three planting densities (high, medium and low), and two seasons (Season one and two). Standard error bar represent standard deviation (±1.7).
5.2.2.2 Stomatal conductance
There were significant differences (P=0.018) observed for stomatal conductance for plant densities.
Stomatal conductance was high for high planting density (351.06 mmol m-2 s-1) when compared
with low planting density (346.00 mmol m-2 s-1) and medium planting density (321.62 mmol m-2 s-
1). There were significant differences (P=0.001) in stomatal conductance for the two growing
seasons. Season one (18.93 mmol m-2 s-1) had a higher stomatal conductance when compared with
season two (8.70 mmol m-2 s-1). These were also in line with soil water content results across the
seasons. Variety x season x water regime had significant effects on stomatal conductance
0
5
10
15
20
25
30
35
40
45
50
Season1
Season2
Season1
Season2
Season1
Season2
Season1
Season2
Season1
Season2
Season1
Season2
High Low Medium High Low Medium
Irrigated Rainfed
Chl
orop
hyll
Con
tent
Inde
x (C
CI)
Water regime
P=0.013; LSD(P>0.05)=3.4; CV=3%
Gadra Malelani Mtata
43
(P=0.045). The interaction showed that between two water regimes irrigated was lower (337.00
mmol m-2 s-1) when compared with rain-fed (341.65 mmol m-2 s-1) (Figures 5.2 and 5.3) (Appendix
9).
Figure 5.2: A comparison of stomatal conductance for three planting densities (high, medium, and low). Standard error bar represent standard deviation (±9.91).
280
290
300
310
320
330
340
350
360
370
High Medium Low
Stom
atal
con
duct
ance
(mm
ol m
-2s-1
)
Plant Density
P=0.018; LSD(P>0.05)=19.8; CV=2.4
44
Figure 5.3: A comparison of stomatal conductance for two growing seasons (Season one and two), two water regimes (irrigated and rain-fed), and three dry bean varieties (Malelane, Gadra and Mtata). Standard error bar represent standard deviation (±13.4).
5.2.3 Crop growth
5.2.3.1 Field emergence
An interaction of water regime x variety and plant density had no significant differences (P>0.05)
on dry bean emergence. However, water regime had significant differences (P=0.025) on
emergence. The irrigated field had the highest emergence (70.00 %) relative to rain-fed (61.70 %)
(Figure 5.4). There were significant differences (P = 0.001) observed for emergence for three dry
bean varieties. Mtata had the highest emergence (75.20%) while Malelane and Gadra had a
germination percentage of 64.30% and 58.00%, respectively (Figures 5.4 and 5.5) (Appendix 10).
0
100
200
300
400
500
600
700
Gadra Malelani Mtata Gadra Malelani Mtata
Season 1 Season 2Stom
atal
con
duct
ance
(mm
ol m
-2s-1
)
Season
P=0.045; LSD(P>0.05)=26.8; CV=2.4%
Irrigated Rainfed
45
Figure 5.1: A comparison of final emergence for two water regimes (irrigated and rain-fed).
Standard error bar represent standard deviation (±3.58).
10
20
30
40
50
60
70
80
90
100
Irrigated Rainfed
Em
eerg
ence
Water regime
P=0.025; LSD (P>0.05)=7.16; CV=1.9%
46
Figure 5.4: A comparison of final emergence for three dry bean varieties (Malelane, Gadra and Mtata). Standard error bar represent standard deviation (±4.38).
5.2.3.2 Leaf number
Plant density x growth season had significant effect on leaf number (P=0.008) (Appendix 11).
Season one had a higher leaf number (6.80) compared to season two (3.90) (Figure 5.6). There was
a slight difference under plant densities for leaf number with high planting density having a high
leaf number (4.09) when compared to medium planting density (4.00) low planting density (3.80).
For water regimes irrigated field had a higher leaf number (5.85) when compared to rain-fed field
(4.94). With the varieties, Mtata had the highest leaf number (5.72) when compared with Gadra
(5.69), and Malelane (4.82) under the two water regimes irrigated and rain-fed. Treatment
combination season one, high density had the highest leaf number when compared with low density
under two seasons with lowest leaf number (Figures 5.6 and 5.7).
0
10
20
30
40
50
60
70
80
90
100
Gadra Malelani Mtata
Em
erge
nce
Variety
P=0.001; LSD(P>0.05)=8.76; CV=1.9%
47
Figure 5.5: A comparison of final leaf number for three dry bean varieties (Mtata, Malelane and Gadra). Standard error bar represent standard deviation (±0.17).
Figure 5.6: A comparison of final leaf number for plant density (high, medium and low) at two seasons (Season one and two). Standard error bar represent standard deviation (±0.32).
0
1
2
3
4
5
6
7
Gadra Malelani Mtata
Lea
f num
ber
Cultivar
P=0.001; LSD(P>0.05) = 0.34; CV = 3.1%
0
1
2
3
4
5
6
7
8
High Medium Low
Lea
f num
ber
Plant density
P=0.008; LSD(P>0.05) = 0.64; CV = 3.1%
Season 1 Season 2
48
5.2.3.3 Plant height
Season x plant density x water regime x variety had significant effect on plant height (P=0.013)
(Appendix 12). Season one had the highest plant height (18.91) when compared with season two
(8.27) (Figure 5.8). This was contributed by that season one had optimum environmental conditions
for dry beans production. For water regimes, irrigated had a high plant height when compared with
rain-fed. Across all treatments combinations, Gadra had a high plant height (26.63) when compared
with Malelane which had lowest plant height (5.83). The interaction of water regime and seasons
showed that season one under both water regimes (irrigated and rain-fed) had the highest plant
height relative to season two which had a low plant height (Figure 5.8).
Figure 5.7: A comparison of plant height for two growing seasons (Season one and two) and two water regimes (irrigated and rain-fed), three plant densities (high, medium and low), and three dry bean varieties (Malelane, Gadra and Mtata ). Standard error bar represent standard deviation (±1.2).
0
5
10
15
20
25
30
Gad
ra
Mal
elan
i
Mta
ta
Gad
ra
Mal
elan
i
Mta
ta
Gad
ra
Mal
elan
i
Mta
ta
Gad
ra
Mal
elan
i
Mta
ta
Gad
ra
Mal
elan
i
Mta
ta
Gad
ra
Mal
elan
i
Mta
ta
High Medium Low High Medium Low
Irrigated Rainfed
Plan
t hei
ght (
cm)
Water regime
P=0.013; LSD(P>0.05) = 2.4; CV = 1.9%
Season 1 Season 2
49
5.2.3.4 Leaf Area Index
There were significance differences (P=0.044) final leaf area index under three planting density
(Appendix 13). A higher leaf area index was under high planting density (0.35) when compared
with medium planting density (0.30) and low planting density (0.20). Water regime had significant
effect (P = 0.001) on final leaf area index (Appendix 13). Irrigated had a high leaf area index (0.33)
when compared with rain-fed (0.24). The same was observed on low leaf number and soil water
content under rain-fed water regime. Season had significant effect (P=0.001) on final leaf area
index. Between the two seasons, the results showed that season one had a high leaf area index
(0.52) when compared with season two (0.048). However, there were no significant differences
(P>0.05) observed for dry bean varieties. There were significance differences (P=0.006) for final
leaf area index for water regime x season. The irrigated treatment had a high leaf area index (0.32)
when compared to rain-fed (0.24) (Figures 5.9 and 5.10) (Appendix 13).
Figure 5.8: A comparison of leaf area index (LAI) for two seasons (Season one and two), and three planting densities (high, medium and low). Standard error bar represent standard deviation (±0.055).
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
High Low Medium
Lea
f Are
a In
dex
(LA
I)
Plant density
P=0.001; LSD(P>0.05) = 0.11; CV = 10.1%
Season 1 Season 2
50
Figure 5.9: A comparison of leaf area index (LAI) for two seasons (Season one and two), and two water regimes (irrigated and rain-fed). Standard error bar represent standard deviation (±0.033).
5.2.3.5 Intercepted Photosynthetically Active Radiation (PAR)
There were significance differences (P=0.024) final intercepted photosynthetically active radiation
PAR two water regimes (Appendix 14). The irrigated field had a high leaf area index (217.5 W m-
2) when compared with rain-fed (160.14 W m-2). There were significance differences (P=0.001) for
final intercepted PAR for two seasons. Season one had a high PAR (324.32 W m-2) when compared
with season two (53.60 W m-2). Planting density had significant differences (P=0.002) for final
intercepted PAR. High density planting density had a high intercepted PAR (234.40 W m-2) when
compared with medium planting density (192.42) and low planting density (140.22 W m-2). There
were significance differences (P=0.008) final intercepted PAR, water regime x season. For the
water regime, irrigated field had high intercepted PAR (217.15 W m-2) when compared with rain-
fed (160.40 W m-2). Seasons one had a high intercepted PAR (324.20 W m-2) when compared with
season two (53.16 W m-2). Season one had high intercepted PAR (324.20 W m-2) when compared
with season two (53.60 W m-2) (Figures 5.11 and 5.12).
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Season 1 Season 2
Lea
f Ara
e In
dex
(LA
I)
Season
P=0.006; LSD(P>0.05) = 0.066; CV = 10.1%
Irrigated Rainfed
51
Figure 5.10: A comparison of intercepted photosynthetically active radiation (PAR) (W m-2) for two growth seasons (season one and two) and two water regimes (irrigated and rain-fed). Standard error bar represent standard deviation (±20.13).
0
50
100
150
200
250
300
350
400
450
Season 1 Season 2
Inte
rcep
ted
PAR
(W
m-2
)
Season
P=0.008; LSD(P>0.05)=40.26; CV=5.7%
Irrigated Rainfed
52
Figure 5.11: A comparison of intercepted photosynthetically active radiation (PAR) (W m-2) for three planting densities (high, medium and low), and growth seasons (Season one and two). Standard error bar represent standard deviation (±27.72).
5.2.3.6 Flowering percentage
There were significance differences (P=0.001) for final flower percentage for three dry bean
varieties (Appendix 15). Gadra had a high flower percentage (50.43%) when compared with Mtata
(48.33%) and Malelane (42.23%). Seasons also showed significant differences (P=0.001) with
respect to flower percentage. Season one had a high flower percentage (78.19%) when compared
with seasons two (15.06%). There were no significant differences (P>0.05) for plant densities. An
interaction of season and water regime had significance differences (P=0.003) on flower
percentage. Season one had a high flower percentage (78.09%) when compared with season two
(15.06%). Between the two water regimes rain-fed had a high flowering percentage (49.21%) when
compared with irrigated (44.48%) (Figures 5.13 and 5.14).
0
50
100
150
200
250
300
350
400
450
500
High Low Medium
Inte
rcep
ted
PAR
(W m
-2)
Plant density
P=0.002; LSD(P>0.05)=55.43; CV=5.7%
Season 1 Season 2
53
Figure 5.2: The evaluation of flower percentage for three dry bean varieties (Mtata, Gadra and
Malelane). Standard error bar represent standard deviation (±1.85).
Figure 5.3: The evaluation of flower percentage for two seasons (Season one and two) and under
two water regimes (irrigated and rain-fed). Standard error bar represent standard deviation (±2.65).
0
10
20
30
40
50
60
Gadra Malelani Mtata
Flow
erin
g
Cultivar
P=0.001; LSD(P>0.05)=3.7; CV=4.3%
0102030405060708090
Season 1 Season 2
Flow
erin
g
Season
P=0.003; LSD(P>0.05)=5.3; CV=4.3%
Irrigated Rainfed
54
5.2.4 Yield and yield parameters
5.2.4.1 Biomass
Planting density had significant effect (P=0.002) on biomass (Appendix 16). Biomass was higher
for high planting density (284.5 g) when compared with medium planting density (176.5 g) and
low planting density (102.00 g). There were significant differences (P=0.001) observed final
biomass, over season one and two. Season one had a high biomass (371.00 g) when compared with
season two (10.00 g). There were no significant differences (P>0.05) observed amongst the three
dry bean varieties in terms of final biomass. There were significant differences (P=0.001) observed
final biomass, treatment combination growth seasons x plant density. Season one had the highest
biomass (371.00 g) compared to season two (4.00 g). High biomass was observed under high
planting density (284.50 g) when compared with medium planting density (176.50 g) and low
planting density (102.00 g) (Figure 5.15).
Figure 5.4: A comparison of final biomass for two seasons (Season one and two) and three plant
densities (high, medium and low). Standard error bar represent standard deviation (±37.70).
0
100
200
300
400
500
600
700
High Low Medium
Bio
mas
s (g/
plot
)
Plant density
P=0.001; LSD(P>0.05)=75.4; CV=12.8%
Season 1 Season 2
55
5.2.4.2 Grain yield
Planting density had a significant effect (P=0.008) on final grain yield (Appendix 17). High
planting density had a high grain yield (71.12 g/plot) when compared with medium planting density
(51.01 g/plot) and low planting density (34.47 g/plot). There were significant differences (P=0.001)
observed for final grain yield on two growth seasons. Season one had a high grain yield (103.51
g/plot) when compared with season two (1.20 g/plot). Grain yield showed that there was
significance differences (P=0.001) among the three dry bean varieties. Gadra had a high grain yield
(75.39 g/plot) when compared with Malelane (42.82 g/plot) and Mtata (42.18 g/plot). There were
significance differences (P=0.001) final grain yield on planting density x variety. High planting
density had a high grain yield (71.52 g/plot) when compared with medium planting density (51.11
g/plot) and low planting density (34.70 g/plot). Season x variety had significant effect (P = 0.001)
on grain. Season one had a high grain yield (103.20 g/plot) when compared with season two (1.20
g/plot) (Figure 5.16 and 5.17).
Figure 5.5: A comparison of final grain yield for three dry bean varieties (Mtata, Gadra and
Malelane) and plant density (high, medium and low). Standard error bar represent standard
deviation (±13.58).
0
20
40
60
80
100
120
Gadra Malelani Mtata
Gra
in y
ield
(g/p
lot)
Cultivar
P=0.001; LSD(P>0.05)=27.16; CV=16.3%
High Low Medium
56
Figure 5.6: A comparison of final grain yield for three dry bean varieties (Mtata, Gadra and
Malelane) and under two seasons (Season one and two). Standard error bar represent standard
deviation (±10.35).
5.2.4.3 Harvest Index
Variety had significant effect (P=0.001) on harvest index (Appendix 18). Gadra had higher harvest
index (20.7%) when compared with Malelane (13.12%) and Mtata (9.99%). There were significant
differences (P=0.001) final harvest index on water regimes. Irrigated had higher harvest index
(29.05%) when compared with rain-fed (0.23%). Water regime x season had significant effect (P
= 0.001) on final harvest index. Season one had higher harvest index (27.00%) when compared
with season two (2.00%). Planting density x season had significant effect (P=0.005) on harvest
index. Low density had high harvest index (16.71%) when compared with medium (14.55%) and
high density (12.62%) (Figures 5.18, 5.19 and 5.20).
0
20
40
60
80
100
120
140
160
180
Gadra Malelani Mtata
Gra
in y
ield
(g/p
lot)
Cultivar
P=0.001; LSD(P>0.05)=20.7; CV=16.3%
Season 1 Season 2
57
Figure 5.7: A comparison of harvest index (HI) for two water regimes (irrigated and rain-fed) and
two seasons (Season one and two). Standard error bar represent standard deviation (±1.15).
0
5
10
15
20
25
30
35
Season 1 Season 2
Har
vest
Inde
x (%
)
Season
P=0.015; LSD(P>0.05)=2.3; CV=4.3%
Irrigated Rainfed
58
Figure 5.8: A comparison of harvest index (HI) for two seasons (Season one and two seasons) and
three planting densities (high, medium and low). Standard error bar represent standard deviation
(1.95).
Figure 5.9: A comparison of harvest index (HI) for two seasons (Season one and two) and three
varieties (Malelane, Gadra and Mtata). Standard error bar represent standard deviation (±1.7).
0
5
10
15
20
25
30
35
40
High Low Medium
Har
vest
Inde
x (%
)
Plant density
P=0.005; LSD(P>0.05)=3.9; CV=4.3%
Season 1 Season 2
05
101520253035404550
Gadra Malelani Mtata
Har
vest
inde
x (%
)
Cultivar
P=0.001; LSD(P>0.05)=3.4; CV=4.3%
Season 1 Season 2
59
5.2.5 Crop water use and water use efficiency
Crop water use for three dry bean varieties Malelane had a high crop water use (320.42 mm) when
compared with Gadra (287.19 mm) and Mtata (283.54 mm). Water use efficiency was high for
Gadra (0.0037 kg m-3) when compared with Malelane (0.00091 kg m-3) and Mtata (0.00088 kg m-
3). For water regimes, crop water use was high for irrigated (329.92 mm) and relatively low for
rain-fed (263.50 mm). Water use efficiency was low for rain-fed (0.0013 kg m-3) when compared
with irrigated (0.0024 kg m-3). Crop water use for plant density was high for medium planting
density (310.86 mm) when compared with high (291.83 mm) and low planting density (287.47
mm). Water use efficiency for plant density was high for medium planting density (0.0031 kg m-3)
when compared with high planting density (0.0016 kg m-3) and low planting density (0.00083 kg
m-3) (Table 5.2).
Table 5.2: Crop water use, yield and water use efficiency comparisons for dry bean varieties
(Mtata, Gadra and Malelane), water regimes (irrigated and rain-fed), and plant density (high,
medium and low).
Variety Plant density Water regime Crop water use (mm)
Water use efficiency (kg m-3)
Gadra
Low Rain-fed
249.18 0.0011 Medium 276.38 0.0021 High 265.70 0.0020 Low
Irrigated 290.76 0.0013
Medium 351.98 0.0131 High 289.12 0.0026
Malelane
Low Rain-fed
274.25 0.0010 Medium 307.04 0.0011 High 289.11 0.0014 Low
Irrigated 347.71 0.0004
Medium 351.00 0.0006 High 347.46 0.0009
Mtata
Low Rain-fed
247.68 0.0007 Medium 215.25 0.0009 High 247.07 0.0010 Low
Irrigated 315.22 0.0004
Medium 363.50 0.0007 High 312.53 0.0017
*Values of crop water use, yield and water use efficiency were not replicated. Therefore, values presented in the table are means of treatment combinations.
60
5.3 Discussion
Soil water content for growth seasons was observed to be higher under season one when compared
with season two. Seasonal variations in the soil water content were due to the fact that under season
one there were optimal weather conditions namely rainfall, hence the soil received adequate
amounts of water (Gómez-Plaza et al., 2001). Treatment combination of medium planting density
under both growing seasons had a high soil water content. Hence, this combination can be
suggested for dry bean production under season one and two.
Irrigation under season one and two had a high soil water content when compared with rainfed.
This can be explained by that water was received through irrigation, hence, rain-fed had water
stress, therefore, lower soil water content (Brevedan et al., 2012). Furthermore, crop water use and
water use efficiency was high for irrigated and relatively low for rain-fed. According to Mathobo
et al. (2017), WUE was high under occasionally irrigated field. Crop water use and water use
efficiency varied amongst the dry bean varieties. Different dry bean variety choice as they had
different adaptability towards water stress, root structure and metabolic rate (Chaves et al., 2002)
.Malelane had a high crop water use when compared with Gadra and Mtata and water use efficiency
was high for Gadra when compared to Malelane and Mtata. Thus, supporting that different dry
bean varieties had varied adaptability. The results showed that the optimum agronomic
management practices were medium planting density that had high water use efficiency compared
with low and high planting density.
Water regime had significant effect (P=0.025) on final emergence. The differences were similar to
those observed for soil water content whereby irrigated treatment had high emergence when
compared with rainfed. This suggests that high water content under season one influenced crop
stand when compared with rainfed which most likely was under water stress resulted in low
emergence. Suggesting that water availability influences final crop stand establishment (Brevedan
et al., 2012). This supports that water is required for good crop emergence (Department of
Agriculture, 2010). A study done by Brevedan et al. (2012) showed that under reduced water
potential, reduced shoot length on lovegrass. Futhermore, a similar trend was observed for
different variety responses towards emergence under the plant growth conditions.
Interaction of variety x water regime had a significant affect (P=0.013) dry bean chlorophyll
content (CCI). Across the planting seasons, the highest chlorophyll content index of was observed
for season one relative to season two. This was due to optimum environmental conditions of season
61
one relative to season two. In which supports that optimum growth season had positive influence
on maize crop production (Ma et al., 2007). Higher CCI suggest that the plant had a high
photosynthetic rate leading to high plant growth and yield components (Chaves et al., 2002).
However, rainfed field had lower CCI due to water stress, meaning the plants had water stress
defence mechanism by lowering the metabolic rate/photosynthesis rate, hence, the low CCI
(Chaves et al., 2002). A study done by Mathobo et al. (2017) showed that under water stress leaf
function is reduced and, therefore, low chlorophyll content. Variety x season x water regime had
significant effect (P=0.045) on final stomatal conductance. An interaction between the two water
regimes showed that irrigation treatment had a lower stomatal conductance when compared with
rain-fed (Figure 5.3).
Interaction of plant density x plant growth seasons had significant differences (P=0.008) observed
for leaf number. Season one had a higher leaf number when compared with season two. Thus,
supporting that the high soil water content under season one and for irrigated had influence on plant
growth. Water regimes results showed that irrigated field had a higher leaf number compared to
rainfed field. Hence, water availability had positive influence on plant growth. Irrigated treatment
had higher water use efficiency, therefore, explaining high leaf number observed from the leaf
number results. According to Poni et al. (2015) reduced leaf number was induced by water stress.
Treatment combination season one x high density had the highest leaf number when compared with
low density x season two had lower leaf number (Figure 5.7). Significant differences (P = 0.013)
for the interaction of season x plant density x water regime x cultivar were observed for plant
height. Plant height results had similar trend as those of leaf number in terms of treatment effects
on plant height.
An interaction of water regime x season had significance differences (P=0.006) for final leaf area
index. The observed trend was similar as for plant height. As water stress lead to reduced leaf area
index (Mathobo et al., 2017). Water regime x season had significant effect (P=0.008) on for final
intercepted PAR. The observed results were similar as that of leaf area index. Water stress caused
a lower intercepted PAR due to the lowered leaf area index.
An interaction of season and water regime had significance differences (P=0.003) on plant
flowering percentage. Seasons had similar effects on flowering as the above mentioned parameters.
However, flowering percentage was higher under rainfed when compared with irrigated trials and
62
earlier flowering is characteristic of drought escape mechanisms (Fenta et al., 2012). Hence, higher
flowering percentage observed under rainfed was due to the limited water conditions.
5.4 Conclusion
The investigation showed that dry bean growth and productivity is responsive agronomic
management practices (dry bean varieties, plant density, season, and water availability). The
variability among the three dry bean cultivars confirmed the initial hypothesis that variety selection
is critical. The results show that soil water content highly influenced plant growth. Planting date
highly influenced water availability. Planting date (season), and water regime showed to be one
universal factor with an impact on growth and yield parameters. The results of the study confirmed
that agronomic practices such as variety and planting date selection, planting density and water
availability have an effect on crop growth and productivity. The results of this study could
contribute to the development of best management practices to assist farmers improve productivity,
especially under rainfed conditions.
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CHAPTER SIX
6.1 General Discussion
Opportunities for improving dry bean production exist through the use of water quantity and
agronomic management practices. These include the use of appropriate planting dates, plant
densities and adaptable varieties.
The key findings of the study were that seed quality for pre– and post–planting dry beans varied
among varieties with Mtata, Malelane and Gadra, having varied responses when subjected to the
varied agronomic conditions. Seed quality parameters test varied significantly among varieties,
plant densities, and water availability with high significant differences observed between two
planting seasons. The results showed that planting in summer was ideal for dry production. It was
observed that seed germination, GVI, and MGT was low under rain-fed conditions. This showed
that the varieties under review had similar disadvantages over water stress as those used by
smallholder farmers who mostly practice rain-fed farming and retain seed for planting in the next
season.
Overall, the study confirmed that agronomic management practices are an important crop
production factor as they influence crop growth, physiology and yield. Therefore, careful and
appropriate selection of agronomic practices is best suited to farmers’ environment critical to a
successful crop production. Since smallholder farmers typically retain seed from the previous
harvest for planting in the subsequent season, appropriate selection of planting date is key to
attaining high quality seed. Inappropriate planting date selection could lead to poor seed quality
thus negatively affecting the subsequent season’s crop.
6.2 Conclusions
The study confirmed that agronomic practices that the maternal plant was exposed to affected plant
growth, physiology and yield; and therefore, subsequent seed quality. The study also showed that
all varieties were adapted to rain-fed conditions, thus, making them ideal for production in rain-fed
agro-ecologies. The effects of planting date and water regime had almost similar effect on crop
growth, physiology and yield. Thus, planting date and water regime should be managed in
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conjunction with each other. Under rain-fed conditions, appropriate planting date influence water
availability during the season. The results suggested that dry bean production was more suited to
grow adaptable under season one when compared with second season as dry bean failed to produce
yield due to low and sub-optimum temperatures. Seed quality is a function of production
environment. Thus, the use of best management is critical to producing seed of high quality. The
fact that dry bean seed quality was relatively high under rain-fed production is encouraging for
smallholder farmers who practice rain-fed agriculture.
6.3 Recommendations
The following recommendations can be made based on this study’s findings:
• the use of good agronomic management practices, through best management practices, is
recommended as it leads to high yields. Farmers should seeks advisory services to obtain
information on the best management practices suited to their specific agro-ecologies;
• subsequent seed quality is heavily linked to how maternal plants were managed i.e. quality
is grown in the field. Again, the use of good agronomic practices such as proper planting
date selection and plant density is strongly encouraged for farmers who wish to retain seed
for subsequent seasons;
• farmers practising rain-fed production can produce seed of good quality given that they
adhere to best management practices; and
• future research should elucidate more on the effect of agronomic practices on subsequent
seed quality, paying special attention to seed physiology and the acquisition of seed quality
i.e. sugar profiles and protein analyses.
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APPENDICES
APPENDIX 1: Analysis of variance table for germination percentage.
1) Variate: Germination_% Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 3 167.33 55.78 1.70 Rep.*Units* stratum Variety 2 304.00 152.00 4.63 0.027 Day 1 80.67 80.67 2.46 0.138 Variety.Day 2 5.33 2.67 0.08 0.922 Residual 15 492.67 32.84 Total 23 1050.00
APPENDIX 2: Analysis of variance table for Germination Velocity Index (GVI).
2) Variate: GVI Source of variation d.f. s.s. m.s. v.r. F pr. Rep stratum 3 10.458 3.486 1.70 Rep.*Units* stratum Variety 2 19.000 9.500 4.63 0.027 Day 1 5.042 5.042 2.46 0.138 Variety.Day 2 0.333 0.167 0.08 0.922 Residual 15 30.792 2.053 Total 23 65.625
APPENDIX 3: Analysis of variance table for germination percentage.